Heating and air conditioning systems for residences, industrial factories, and office buildings involve large cross-sectional header pipes, usually rectangular insulated sheet metal tubular structures, and a large number of smaller branch lines, usually round insulated sheet metal tubular pipes, leading to vents to distribute the heated or cooled air to the desired spaces inside the building. The typical prior art structure for connecting the branch line to the header involves inserting a short length of pipe into a hole cut in the header to receive the pipe, and fastening the pipe in place by any of a variety of means, and then covering all exposed metal surfaces with a suitable insulation. One means for fastening may involve L-shaped brackets attached to both the header and the pipe with bolts and nuts. Another means is to employ a pipe connection with dovetail cut-out fingers on the end which is inserted into the header, and manually bending the dovetails outward to hold the pipe in place. None of these procedures and structures is entirely satisfactory because the resulting connection is so loose that too much air is lost by leakage.
It is an object of this invention to provide an improved device for connecting branch lines to header lines in air conducting systems. It is another object of this invention to provide a tight connection which eliminates leaks in air conductor piping. Still other objects will become apparent from the more detailed description which follows.